First Degree Heart Block

First Degree Heart Block Definition

PR interval > 200ms (five small squares)

  • Marked’ first degree block if PR interval > 300ms
  • Does not cause haemodynamic disturbance
  • No specific treatment is required
ECG Rhythm strip PR interval prolonged 1st degree AV block

Causes of First Degree Heart Block


ECG Examples

Example 1
ECG Rhythm strip PR interval prolonged extreme 1st degree AV block
  • Marked first degree heart block
  • PR interval > 300 ms, P waves are buried in the preceding T wave

Example 2
ECG 1st degree AV block 1
  • Sinus bradycardia with 1st degree AV block
  • PR interval > 300 ms

Example 3

ECG 1st degree AV block 2
  • Normal sinus rhythm with 1st degree AV block
  • PR interval 260 ms

Related Topics


LITFL Further Reading

Advanced Reading

ECG LIBRARY 700

ECG LIBRARY

Electrocardiogram

Emergency Medicine Specialist MBChB FRCEM FACEM. Medical Education, Cardiology and Web Based Resources | @jjlarkin78 | LinkedIn |

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